Smoke – it's the signature flavour behind some of the world's most popular whiskies, yet many of us are completely unaware of how it even gets tfhere in the first place.

Smoke gives the whiskies of the Scottish west coast and islands their maritime quality, their often intense sootiness and a medicinal aroma which kept them flooding into the US during Prohibition due to a legal loophole. For many it's the most intriguing and appealing character of Scotch, and it's all thanks to something the Scots dig out of the ground called peat.

Peat not Pete

No, peat isn't the name of the whisky-soaked Scotsman you'll find holding up a corner of the bar, but rather a kind of squishy pre-pubescent coal found in bog lands around the world. It's a traditional form of fuel in Scotland, especially in the Hebridean islands off the west coast where trees have long been relatively scarce.

Peat forms in wetland areas from decayed vegetation such as sphagnum moss and ferns. As these areas flood, the vegetation is cut off from oxygen so the rate of its decay is very much slowed. Peat gatherers will cut into banks of this ancient turf during the spring. The bricks they carve out are dried and used to fire the kilns that dry the barley during the malting process. Smoke which comes into contact with the moist grain during this process is retained right through the whisky-making magic – through milling, mashing, fermentation, distillation and even ageing.

You can roughly divide the smoky flavours that peat imparts into a whisky into three main categories, which some malts will express more than others. The first kind of smoke that comes to mind is your classic BBQ smokiness with an almost sweet richness to it. This sort of smoke can sometimes be more reminiscent of a smouldering hearth, or at other times that hearth's sooty sweepings in more intense drams.

The second kind of smokiness, for me, reveals itself as an earthiness – like freshly tilled soil. This can lead to a slightly brackish, almost briny quality in some drams.

The third main quality is all to do with peat's natural phenol compounds, which have long been known to have antiseptic qualities. 'Phenol' forms the 'P' in TCP (trichlorophenylmethyliodosalicyl), a popular form of antiseptic – especially in the UK. It goes a long way to explain why some of the more intensely-peated whiskies from the isle of Islay have an aroma often described as 'medicinal', 'antiseptic' or even 'bandages'. Sometimes these aromas appear to be more oily and can reveal whiffs of boot polish or burnt rubber; but that's a great thing if you like smoky whisky – really!

PPM

The smokiness of Scotch whisky is measured in PPM, or phenols parts per million. A liquid with a PPM of one would need one molecule to be diluted over one million times before it became undetectable.

A lot of whisky producers don't get too hung up on talking about the PPM of their whiskies and some PPM levels are the levels of the malted barley rather than the finished and aged product. Both distillation and prolonged ageing do significantly reduce the final PPM. When it all comes down to it, the proof is on the palate – a quick sample will tell you whether or not this is for you.

Peat under attack

According to the Scottish Parliament Information Centre, Scotland has about 60 per cent of the UK's peatlands, with 20 per cent of Scotland's land area covered by peat-rich blanket bogs alone. Scottish peats are estimated to hold around 1620 mega-tonnes of carbon, but despite these staggering stats there's a real fear that the Scotch whisky industry may lose this vital smoking ingredient.

On June 24 the Herald Scotland reported that number of powerful environmental groups have called for a ban on commercial extraction of peat by 2020. Members of Scottish Environment Link – including the Scottish Wildlife Trust, RSPB and the John Muir Trust - claim that ending commercial peat use is essential to slow the decline in Scotland's biodiversity of plant life and animal species.

The amount of carbon being released from peat bogs around the globe – especially from giant peat fires in Indonesia – is truly a serious environmental concern. And losing a fine smoky dram might be climate change's next major toll.

Would you be willing to forgo savouring a smoky malt in favour of saving the shrinking polar ice caps?